Update to FAQ 4.15 (cannot logon) - how I solved the problem

I had the FAQ C.8 problem -- could not logon!
The current answer did not resolve my problem.

I found the answer with PHP sessions storage directory at http://www.php.net/manual/en/ref.session.php: session.save_path ....
"Note: Windows users have to change this variable in order to use PHP's session functions. Make sure to specify a valid path, e.g.: c:/temp."

I corrected my session save directory in php.ini, restarted IIS and suddenly I could logon!